Various surgical procedures are routinely carried out intravascularly or intraluminally. For example, in the treatment of vascular disease, such as arteriosclerosis, it is a common practice to invade the artery and insert an instrument (e.g., a balloon or other type of catheter) to carry out a procedure within the artery. Endovascular therapy has been used to treat different conditions. Such treatments include control of internal bleeding, occlusion of blood supply to tumors, and occlusion of aneurysm. Often the target site is difficult to reach. Catheters are increasingly becoming components of endovascular therapies because of their ability to access remote regions of the human body and deliver diagnostic or therapeutic agents. Catheters are often introduced into large arteries, such as those in the groin or in the neck, and then passed through narrowing regions of the arterial system until reaching the selected target site. Catheters are often stiffer at their proximal end to allow the pushing and manipulation of the catheter as it progresses through the body, but sufficiently flexible at the distal end to allow passage of the catheter tip through the body's blood vessels.
In order to maneuver around turns and bends in the vasculature, an operator may observe the catheter fluoroscopically and selectively deflect the tip and rotate the proximal end of the catheter shaft. The ability to control the precise position of the distal end of the catheter depends on the catheter's ability to transmit forces exerted at the proximal end to the distal end. Without proper rotational and longitudinal force transmission, the operator may be unable to control precisely the catheter tip and, consequently, the operating procedure may be delayed or less effectively performed.